MATERIALS FOR PLAIN CONCRETE

Question 1

Describe briefly the cement manufacturing process

Answer 1

to grinding limestone and clay into a very fine powder, mixing them carefully in certain proportions and burning them in a large rotary clin at a temperature about 1400 C when the materials sinters and partially fuses into clinker. The clinker is cooled and ground to a fine powder, with some gypsum added, and the resulting product is Portland cement or ordinary cement

Question 2

Name the four most important cement types used in Sweden

Answer 2

• Standard Portland cement
• Byggcement (mixture between Portland cement and limestone filler)
• Snabbhärdande portlandcement
• Anläggningscement

Question 3

The quality of a portland cement can me influenced in mainly two ways. Name these

Answer 3

• By the composition of the clinker-component

- By the fineness of the grinding of the clinker

Question 4

The reaction between cement and water is also called exothermic reaction. What does this mean?

Answer 4

When water and cement is mixed, the reaction will produce heat which is transferred to the surrounding.

Question 5

Present diagrams showing the relationship between strength development and time for SH-cement, STD-cement and LH-cement

Answer 5

page 7

Question 6

As regards the use of water for concrete there is a simple “thumb-rule”. Which?

Answer 6

All drinkable water can be used for concrete.

Question 7

Aggregates for concrete must fulfill some requirements. Name four such requirements. Describe how these requirements normally are fulfilled in Sweden

Answer 7

• Suitability from a petographic point of view
• Strength
• Cleanness
• Size-distribution
  pg. 9

Question 8

Define the concept “sand fraction”

Answer 8

particle-seize 0-4mm

Question 9

Define the concept “cobble fraction”

Answer 9

Particle-seize above 4 mm

Question 10

Define the concept “admixture”

Answer 10

Chemical substances which are added to the concrete at the mixing stage

Question 11

Name five basic types of chemical admixtures for concrete

Answer 11

1. Accelerator
2. Water-reducer (plasticizer)
3. Super-plasticizer
4. Air-entrainingagent

Question 12

Water reducers can be used for different purposes. Describe these purposes

Answer 12

1. to achieve a higher strength by decreasing the water cement ratio at the same workability as an admixture-free mix.
2. To achieve the same workability by decreasing the cement content as to reduce the heat of hydration in mass concrete
3. To increase the workability so as to ease placing in inaccessible